Now let me ask you: which aligns better with these goals, Linux or UNIX-proper?

Although, legally, Free|Open|NetBSD can't be called Unix, codewise it's clearly the modern decendent of Unix and aligns better with those goals. I think that the *BSD OS's clearly carry the Unix flame.

As far as moving to the next level of Unix. That could only be Plan 9. Plan 9 is what you get when the original writers of Unix re-thought things.